An NBR composition is laminated on metal and the laminate is crosslinked (vulcanized) to produce a rubber metal laminate. The rubber metal laminate is used as a gasket material.
As crosslinking (vulcanizing) of a rubber composition, press crosslinking (vulcanizing) and crosslinking (vulcanizing) in an oven have been known. In order to improve productivity, an NBR composition capable of undergoing crosslinking (vulcanizing) in an oven, that is, a sulfur-crosslinking NBR composition is required. Further, the NBR composition is required not to generate nitrosoamine during the crosslinking.
This is because nitrosamine is a controlled item under Technische Regeln fur Gefahrstoffe 552 (TRGS552), German Law setting forth technical regulations on dangerous substances, and also a controlled substance in Pollutant Release AND Transfer Register (PRTR), and therefore the movement of decreased use is increased.
Patent Document 1 has solved the problem of occurrence of nitrosamine during crosslinking by using an NBR composition containing sulfur as a crosslinker and at least one sulfur donor compound selected from tetrabenzylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, zinc tetrabenzyldithiocarbamate, and 1,6-bis(N,N-dibenzylthiocarbamodithio)hexane as a crosslinking agent.